1. Field of the Invention
The present invention relates to a technique for measuring a toner current generated by a transfer of charged toner.
2. Description of the Related Art
Toner is used as image forming particles in image forming devices which employ electrophotography. Image forming devices cause a transfer of toner between members in processes such as developing, copying, and recovery, often utilizing the effects of electric fields to cause the transfer. Measuring the transfer properties of toner in an electric field is, therefore, of importance in terms of the research and development of image forming devices and toner.
The Time of Flight method is known as a conventional method for measuring the transfer properties of charges in members composed of an insulating polymer, etc. The Time of Flight method pre-applies a voltage between opposing electrodes which sandwich the member to be measured, exposes light, an electron beam, X-rays, etc. to the component to cause a generation of a charge, and detects a transfer of the charge, resulting from the voltage, as a current flowing between the electrodes. Using the result of this detection, it is possible to derive transfer properties, such as mobility of the charge, in the member (see chapter 1, pp. 27–30, Experimental Polymer Science New Edition, Vol. 9, “Properties of Polymers (2)—Electrical, Optical, and Magnetic Properties”, Society of Polymer Science, Japan, Kyoritsu Shuppan Co., Ltd.).
However, it is difficult to directly apply the aforementioned Time of Flight method to measuring the transfer properties of toner. If this method were used as is, a voltage could be applied between opposing electrodes after a toner layer is formed on one of the electrodes, and the transfer of the toner as a result of the voltage could be detected as a current flowing between the electrodes. As a result, however, the presence of a capacitance between the opposing electrodes causes a charging current to flow along with the toner current from the application of the voltage. Accordingly, it is impossible to measure only the toner current since any result of the measurement of the current flowing between the electrodes includes the charging current component.